Pre-synchronization method for grid-connection of virtual synchronous generators based micro-grids

Since the photovoltaic power generation, wind power and other distributed power supply are volatile and random, they will affect the stability of the grid frequency. In order to improve the voltage and frequency in micro-grid, the virtual synchronous generator control strategy is proposed for inverter control, which can emulate the behavior of synchronous generator, decrease rate of change of frequency and provide dynamic power support to grid. However, when virtual synchronous generators based micro-grids switch from islanded mode to grid-connected mode, inrush current may deteriorate the power quality of micro-grids and damage the device in micro-grids. This paper discusses the problem of pre-synchronization and presents a new pre-synchronization method for grid-connection of virtual synchronous generators based micro-grids. Accordingly, parameter matching between virtual inertia and capacity among virtual synchronous generators is analyzed in detail. Simulation results show the validation of the proposed method.